Ashnod the Uncaring | Akul the Unrepentant | Cloudstone Curio

(and one other card)

Activate
Akul the Unrepentant by sacrificing three creatures.
Ashnod the Uncaring triggers, copying
Akul the Unrepentant's ability.
Resolve the copy of
Akul the Unrepentant's ability, putting
Abhorrent Overlord from your hand onto the battlefield.
When
Abhorrent Overlord enters the battlefield, it and
Cloudstone Curio trigger.
Resolve the
Abhorrent Overlord trigger, creating a number of 1/1 Harpy creature tokens equal to your devotion to black.
When the Harpys enter the battlefield,
Cloudstone Curio triggers that many times, returning nothing to your hand from the battlefield.
Resolve the
Cloudstone Curio trigger from step 4, returning
Akul the Unrepentant from the battlefield to your hand.
Resolve
Akul the Unrepentant's ability from step 1, putting it onto the battlefield from your hand.
When
Akul the Unrepentant enters the battlefield,
Cloudstone Curio triggers, returning
Abhorrent Overlord from the battlefield to your hand.
Repeat.